Telephone-exchange system.



C. L. GOODRUM.

TELERHONE EXCHANGE SYSTEM.

APPLlCATlON FILED lAN.20,1916.

Patented Feb. 27, 1917;

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" A/fy C. L. GOODRUMM TELEPHONE EXCHANGE SYSTEM.

APPLICATlON FILED JAN. 20, I916.

Patented Feb. 27, 1917.

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CHARLES L. GOODRUM, OF NEW YORK, N. Y., ASSIGNOR T WESTERN ELECTRIC COM-PANY, INCORPORATED, 0F NEXV YORK, N. Y., A CORPORATION OF NEW YORK.

TELEPHONE-EXCHANGE SYSTEM.

Application filed January 20, 1916.

To all whom it may concern:

This invention relates to' telephone 6X-' change systems wherein callinglines are as sociated with idle connecting circuits by means of linefinders.

Its object is to provide a line finder circuit arrangement wherein onlythree terminals per line are necessary, and wherein a line is made totest busy in the connector switches in which it appears, as well ascalling in the finders in which it appears, immediately upon theinitiation of a call in such line.

In accordance with this invention, each line is provided with a line anda cut-off relay, the cut-off relay being connected through a normalcontact of the line relay with the multiple test terminals of such linein the finder and connector banks. The line relay is adapted upon itsenergization to start an idle line finder in motion, to disconnect thecut-off relay from the multiple test terminals and to connect thereto astop relay which is connected to the other pole of the battery from thatto which the cut-off relay is connected. The connection of this stoprelay to the test multiples sets up a calling condition thereon in thefinders and a busy condition thereon in the connectors. When the findertest brush reaches the calling line,

a circuit is closed including the stop relayreferred to, which inenergizing opens the starting circuit to stop the finder upon thecalling line terminals. The stop relay, in addition to opening thestarting circuit, also initiates a circuit change which causes thedeenergization of the line relay. The line relay, in falling back,restores the connection of the cut-off relay to the test multiples inorder that it may be operated over a circuit leading through the finderto remove the control of the line relay from the calling line duringconversation. The finder side switch. in the meantime, has operated toSpecification of Letters Patent.

Patented Feb. 2'7, 1917;. Serial No. 73,218.

place a busy condition on the connecter test multiples in substitutionof that leading through the stop relay.

Referring to the drawings, Figure 1 shows a finder circuit embodying theinvention; and Fig. 2 shows a suitable connector circuit for operatingtherewith.

The invention will be more readily understood from a detaileddescription of the operations involved in setting up a connection.

Upon the removal of the receiver by the calling party at substation A,the following circuit is closed to energize line relay 10: free pole ofbattery, armature and back contact of relay 11, left winding of relay10, left armature and back contact of cut-off relay 12, line conductor13 through the telephonic apparatus at substation A, line conductor 14,right armature and back contact of relay 12, right winding of. relay 10to ground. Relay 10 at its leftarmature and front contact closes thefollowing circuit to energize a relay 15, which is common to the groupof lines to which substation A belongs: free pole of battery, relay 15,conductor 16,- armature and backcontact of relay 17, conductor 18,armature and back contact of relay19, conductor 20, left armature andfront contact of relay 10-,to ground. Assuming thelinefinder normallyserving this line group to be in normal position, the group brush 21 onthe finder brush shaft 42 will be in engagement with multiple contact 22of the line group, in which position of the brush shaft a set ofbrushes, 23, 24, 25 thereon will. be in operative relation to multiples26, 27, 28 of this particular line group. Under such assumption thefollowing circuit is closed for the escapement magnet 29 of the sideswitchof the line finder in parallel with that traced for relay 15: freepole of battery, magnet 29, side switch arm 3 and" the following circuitis closed for the secrelay 15, conductor 16, left armature and frontcontact of relay 15, conductor 18, back contact'of relay 19, conductorto ground, at the left armature and front contact of relay 10. Inposition 2 of the side swltch,

- arm 4 connects battery to test brush of the finder through aresistance 31. a magnet now makes and breaks its circuit in thewell-known manner to advance thebrushes 23, 24, 25, over the multiples26, 27,

The

28. The energizationof the line relay 10 opens the connection ofbattery'through cut-0E relay 12 with finder multiple termi- 'nals 28 andconnector multiples 34 and substitutes therefor ground through relay 19.

Consequently, when the brush 25 reaches the terminal 28 of the callingline, relay 19 becomes energized in the following circuit: free pole ofbattery, resistance 31, arm 4 and its second contact, brush 25, terminal28, conductor 32, right armature and front contact of relay 10, relay 19to ground. Relay 19 by attracting its armature opens the circuit justtraced for the magnet 30, thus stopping the line finder upon the callingline terminals; In position 2 of the side switch, a

' circuit for escapement magnet 29 was closed in parallel with thecircuit for magnet 30, as

follows: free pole of battery, magnet 29, am

" 3 and its second contact, conductor 33, arm

2 and its second contact to ground at the left armature and frontcontact of relay 10.

- 1 Consequently, when relay 19 energizes, it

opens this circuit also, whereupon escapement magnet 29 becomesdenergized. The

escapement magnet 20 is constructed and arranged to move the side switchfrom position 2 to position 3 upon its deenergization. Relay 19 inattracting its armature, also energizes a slow relay 11 over thefollowing circuit: free pole of battery, relay 11, armature and frontcontact of relay 19, conductor 20, left armature and front contact ofrelay 10 to ground. Relay 11, upon energization, opens the circuit ofthe line relay 10, which, in retracting its right armature, restores theconnection of cut-0E relay 12 to test terminal 28. In position 3 of theside switch, arm 4 closes the following circuit for the cut-off relay 12before slow relay 11 becomes denergized: free pole of battery, relay 12,right armature and back contact of relay 10, conductor 32, test terminal28, brush 25, arm 4 and its third contact to ground. Relay 12, uponenergizing, removes the control of relay 10 from the calling line. Arm 4in moving into position 3 grounds the-test multiples 34 of the callingline in mamas the connectors in substitution of that through relay 19.Arm 2 in position 3 ex tends the starter wire 35 to the next idlefinder. The retraction of the right armature of relay 15 restores thecontrol of the starter wire 35 to the other groups. The relay 17 is slowacting, and by maintaining its armature attracted when the finder shownis being set by a call from another group, preventsa line from the groupcontaining substation A from actuating-relay 15. The side switch arms 5and 6 in position 3 extend the calling line to a first selector, thebrushes 36, 37., 38, and terminals 39, 40, 41, only of which are shownsince such structures are well-known in the art. During the operation ofthe finder, relay 17 at its right armature and front contact energizes arelease relay 57 which maintains open the circuit of finder releasemagnet46. Relay 17 is slow acting, and does not retract its armatureuntil after a slow relay at the first selector is energized and groundsconductor 58, in the well-known manner to hold up relay 57.

In case the line finder shown, which is theone apportioned tothis group,is busy, the starter wire 35 is extended by side switch arm 2 to thenext idle finder. In order for such finder to reach a calling line inthe group containing substation A, it is necessary that its brush shaftbe given a primary movement to pick out the calling group. This will be.made clearfrom ,an explanation of the operations involved in causingthe line findershown to connect with a line in another group. Assuming,therefore, that a call has been initiated in another group, this resultsin grounding conductor 35 incomingfroni such group, wh ch results in theclosure of the followmg circuit: free pole of battery, magnet 20, 1tsarmature and back contact, "side switch arms 1, 2 and their firstcontacts, conductor 35, slow relay 17, right armature and back contactof relay 15, conductor 35 to ground at the armature and front contact ofthe calling line relay. The magnet 20' by interrupting its circuit,steps the brush shaft 42 around in search of the callmg line groupmultiple 43, grounded by the operation of a relay of the calling groupcorresponding to relay 15. Consequently, when the brush 21 reaches suchgroup contact, the following circuit is closed for escapement magnet 29:free pole of battery,

magnet 29, arm 3 and its first contact','brush' 21, multiple contact 43of the calling group to ground. Escapement magnet 29 in energ1z 1ng,moves the side switch into position 2, 1n which positiona circuit isclosed for stepping magnet 30 as follows: free pole of battery, magnet30, its armature'and back contact, arms 1 and 2 and their secondcontacts to starter wire 35. A circuit in par-' allel to that justtraced is also closed for magnet 29 by way of arm 3, its second contactand conductor 33. In position 2, arm

4 connects battery through resistance 31 to brush 25. As hereinbeforedescribed, when the brush 25 reaches the test multiple 28 of the callingline, a relay of the calling group corresponding to relay 19 isenergized to remove ground from the starter wire 35. This results in thedeenergization of the escapement magnet 29, which releases the sideswitch'into position 3, and in the opening of the circuit of magnet 30,which stops the finder upon the calling line'terminals.

The first selector brushes 36, 37, 38 are then set under control of thesender S at the calling substation A in operative relation ture and backcontact of relay 201, conductor 202, conductor 50, terminal 39, selectorbrush 36, conductor 53, arm 5 and its third contact, conductor 54,finder brush 23, terminal 26, conductor 13, through the telephonicapparatus at substation A, conductor 14, terminal 27, finder brush 24,conductor 55, arm 6 and its third contact, conductor.

56, brush 37, terminal 40, conductor 51, conductor 203, inner armatureand back contact of relay 201, lower winding of relay 200 to ground.Relay 200 'at its armature and front contact closes a circuit toenergize a slow relay 204. This relay at its left armature and'frontcontact, prepares a circuit for stepping magnet 206, and at its rightarmature and front contact grounds test conductor 205, leading back tothe selector and finder to hold up relays bridged therefrom to maintainopen the release circuits of such switches. The release relay 57 of thefinder only is shown, as this arrangement is well known in the art.

The calling party now operates his sender in transmitting the tens digitof the called number. The sender inrestoring, interrupts the circuit ofrelay 200 in the well-known manner. Each time the armature of relay 200closes its back contact, an impulse is sent to primary stepping magnet206 of the connector. A. slow'relay 207 is included in this circuit,which relay,- unlike the magnet 206, does not respond to the shortinterruptions of the circuit. Relay 207, in attracting its armature,closes a circuit to energize escapement magnet 208 of the side switch,which is arranged to release the side switch upon its deenergization inthe well-known manner. When the sender restores and maintains the relay200 energized, the slow relay'207 becomes deenergized, and in retractingits armature causes the deenergization of theescapement magnet 208. ThisInag-' net thereupon releases the side switch into position 2. Inposition 2, arm 209 of the side switch associates the secondary steppingmagnet 210 with the back contact of the stepping relay 200. The senderis now operated to transmit the units digit of the wanted number. Eachtime the stepping relay 200 retracts its armature an impulse istransmitted to the secondary stepping magnet 210 in a circuit includingthe slow relay 207. This relay, as before, by attracting its armature,energizes the escapement magnet 208. In the circuit of escapement magnet208 is a relay 211, which by attracting its armatures, opens theconnection of conductors 212, 213 with connector brushes 214, 215 toprevent interference with existing calls. hen the sender restores andmaintains the line relay 200 energized, slow relay 207, after aninterval, becomes deenergized, causing the-denergization of es capementmagnet 208 and relay 211, assuming the line selected to be idle. Sideswitch arm 245 in moving into engagement With its third contact groundsmultiples 219 to cause the selected line to test busy. Side switch arm209, in moving into position 3, prepares a circuit for a relay 220,which, when the constantly operating interrupter 221 reaches a metallicsegment, becomes energized and connects the ringing generator 222 to thecalled line. The bell 23-1 of the called line is thereforeintermittently rung to signal the wanted party. Upon the removal of thereceiver-by such party, while the interrupter 221 is upon an insulatedsegment, supervisory relay 201 becomes energized over the followingcircuit: free pole of battery, right winding of relay 201, conductor204, outer "armature and back contact of relay 220, lower armature andback contact of relay 211, brush 215, contact 218,

226, contact 21.7, brush 214, upper armature 'and back contact of relay211, conductor 212, inner armature and back contact of relay 220,conductor 227, conductor 228, left winding of relay 201, to ground. Thisrelay, by attracting its. outer armature, closes the following circuitto energize a relay 223: free pole of battery, arm 209, conductor 229,-relay 223, conductor 230, outer armature and front contact of relay 201,conductors 231, 232, off-normal contact 233 of the connector, to ground.This relay, by attracting itsleft armature, locks itself over conductor235 independently of the armature and contact of relay 201. Relay 223maintains open the circuit of relay 220, thus permanently cutting offthe ringing current. Arms 248, 270 completethe talking circuit 1nposition 3.

Talking current is fed to the calling substation A over the windings ofrelay 200, and to substation B over the windings of relay 201 in thewell-known manner. Relay 201, upon its energization when the calledparty responds, reverses the direction of the current flow in thecalling line, which may .operate a message register.

1 The release of the switches is controlled by the calling party, andoccursupon the replacement of his receiver, which in deenergizing relay200 closes the following circuit for the release magnet 236 of theconnector: free pole of battery, magnet 236, off-normal contact 237,armatures and back contacts of relays 204, 200 to ground. This circuitis opened when the connector reaches its normal position by the openingof off-normal contact 237. The release magnet in energizing restores theside switch in the well-' known manner. Arm 209 of the side switch, inmoving off its third contact, opens the locking circuit of relay 223.The connector apparatus is-now entirely restored. Relay 204 inretracting its armature removes ground from conductor 205, which resultsin the deenergization of the release relays of the selector and'finder.Relay 57 of the finder, in deenergizing, closes the circuit of, releasemagnet 46 of the finder to restore the same. When the finder shaft 42reaches its normal position and opens off-normal spring 59, magnet 46deenergizes.

Assume, however, that the selected line is busy as a called line whenthe connector brushes 214, 215, 216 are set thereon. After the lastinterruption in the line circuit caused by the sender, the relay 207,after an interval, becomes deenergized. A spring 239, controlled by thearmature of this relay, is arranged to engage its contact 240 beforesaid armature breaks contact with said spring. A busy line is one uponthe test terminal 219 of which ground is present, as previouslydescribed. Consequently, when brush 216 engages such busy terminal, thefollowing circuit is closed for the side switch escapement magnet 208 tomaintain the same energized and hold the side switch in position 2: freepole of battery, escapement magnet 208, relay 211, conductor 242, spring239, contact 240, relay 241, spring 243 and its contact, conductor 244,side switch arm 245, conductor 216 to grounded terminal 219. The sideswitch magnet 208 and the relay 241 are thereby maintained energized.Relay 241 at its outer left armature opens the circuit of secondarystepping magnet 210 to prevent the calling party from further operatingthe connector. At its inner left armature said relay connects lay, a

a busy back apparatus 245 to the calling line over the followingcircuit: busy back apparatus 245 conductor 246, said armature and itsfront contact, conductor 247, side switch arm 248 and its second contactto line conductor 203. The right armature, in engaging spring 243,closes a locking circuit for relay 241 independent of side switch arm245 and grounded terminal 219. This circuit is as follows: free pole ofbattery, escapement magnet 208, relay 211, conductor 242, spring 239,contact 240, relay 241, spring 243, right armature of said relay,conductors 248, 232, off-normal contact 233 of the connector to ground.When the calling party restores his receiver to its switchhook, therelease of the switches is effected as previously described inconnection with a successful CalL' When the connector restores, theopening of off-normal contact 233 unlocks relay 241.

Assume now that the selected line is busy by reason of having initiateda call. The multiple terminals 34 thereof are then connected to groundthrough a relay corre* sponding to 19. When the connector is set uponsuch line, an energizing circuit for busy relay 241 is closed includingrelay 19, which latter relay, however, is not energized. From this pointon, the operations are the same as those previously traced in describingthe case where connection is made to a line which is busy by reason ofhaving been connected to by. another connector.

What is claimed is: y

1. In a telephone exchange system, the combination with a callingtelephone line, a line and a cut-off relay therefor, automatic finderswitches, driving circuits therefor, multiple talking andtest terminalsfor said line in said finder switches, said cut-off relay beingconnected, to said test terminals through a normal contact of said linerelay, means for closing the driving circuit of one of said finders uponthe initiation of a call, means for preventing the operation of thecut-off relay of non-calling lines during the movement of said finder, astop relay, said line relay being adapted when energized to disconnectthe cut-off relay from said test terminals and connect thereto said stoprecircuit adapted to energize said stop relay closed by said finder inarriving upon the calling line terminal, said stop relay thereuponopening the finder-driving circuit.

2. In a telephone exchange system, the combination with a callingtelephone line, a line and a cut-off relay therefor, automatic finderswitches, driving circuits for said finders, multiple talking terminalsand a test terminal for said line in said switches, said cut-off relaybeing connected to the free pole of battery on the one side and to saidtest terminals on the other through a normal contact of said line relay,means for closing the driving circuit of one of said finders upon theenergization of said line relay, a stop relay for said finders connectedto the opposite pole of said battery from that to which the cut-offrelay is connected, said line relay being adapted when energized uponthe initiation of a call to disconnect said cut-off relay from said testterminals and connect thereto said stop relay, said test terminalsbeing'ada ted to be connected to 10 my name this 19th day of January A.D. 15

CHARLES L. GOODRUM. I

